In beer production or in the production of other products made from cereals, such as whiskey, kvass, malt extract and the like, lautering of the wort is one of the most important production steps. During lautering, the spent grains contained in the mash are filtered off so that an aqueous solution of the extract substances substantially free of solids, namely the wort, is obtained as an intermediate product.
Whenever the production of beer is mentioned hereinafter, it means all processes that employ a lauter tun. The further description uses the example of beer production.
In typical brewhouse installations, a lauter tun is used for lautering. To be able to filter the mash, a so-called false bottom is arranged in the lauter tun above the bottom of the tun, said false bottom having passage openings for the wort to run off. After the transfer of the mash in the lauter tun, a filtration layer composed of spent grains forms on the false bottom, by means of which the solids contained in the mash can be filtered off and can be separated from the wort. The spent grains remain in the lauter tun as a solid substance, whereas the wort flows downward through the false bottom and is drained from the lauter tun as an intermediate product. Conventional brewing methods prescribe that prior to the mash transfer, i.e. before the mash is pumped into the lauter tun, a so-called false bottom seal must be pumped into the lauter tun. Water, mostly hot water, is used as a typical false bottom seal. This liquid false bottom seal displaces the air from the space between the vessel bottom of the lauter tun and the false bottom prior to the mash transfer. Also, the air can be displaced from the wort collection pipes branching off from the bottom of the lauter tun and/or be displaced from the wort collection tank or the wort collection ring arranged at the end of the wort collection pipes by means of the liquid false bottom seal. Displacement of the air from the lauter tun by the false bottom seal is supposed to prevent the introduction of ambient oxygen into the wort running off because the properties of the wort would be deteriorated by the introduction of oxygen. Furthermore, the trapped air would block the openings of the false bottom, thus hindering filtration.
The introduction of water as a false bottom seal into the lauter tun is disadvantageous because the water of the false bottom seal dilutes the concentration of the wort. Depending on the type of beer to be produced, the water additionally introduced into the wort has to be evaporated later during wort boiling, which causes significant energy costs.
To reduce the negative effect on the wort concentration by the introduction of pure water as a false bottom seal into the lauter tun, DE 10 2010 030 954 A1 proposes introducing, as a false bottom seal, an aqueous medium that has been obtained at a different stage during the brewing process. Said aqueous medium can be in particular the discharge water used for discharging mash from the mash duct to the lauter tun. Since the discharge water itself contains residual extract, the wort concentration is not reduced as strongly as is the case when using pure water as a false bottom seal. However, a negative effect on the concentration of the wort cannot be entirely avoided in this method, either.
To avoid the negative effect on the concentration of the wort, DE 10 2010 030 954 A1 proposes using, as a false bottom seal, an aqueous medium that is provided for cleaning the lauter tun because this medium, too, contains extract, thus at least diminishing the undesired effect of reduction of the concentration.
All known lauter tuns and methods for operating lauter tuns are based on the use of liquid false bottom seals on a water basis. As a consequence, however, an additional degree of water is always mixed into the lautered wort because of the liquid false bottom seal, which is undesired in many cases. Moreover, the known lauter tuns for reducing said effect require a significant additional effort in installation.